Conventionally, an electric power steering device having an angle sensor to detect a steering angle of a steering wheel has been known. For example, in a Patent Literature (JP 5339094 B), an angle sensor includes a motor rotational angle sensor that detects a rotational angle of an electric motor, and the angle sensor calculates a rotational angle of a steering shaft based on the rotational angle of the electric motor that is detected by the motor rotational angle sensor. Further, in the Patent Literature, to reduce electric consumption, electric power is intermittently supplied to the angle sensor from the battery.